We study the existence of periodic solutions for a nonlinear system of nth-order differential equations on time scales. Assuming a suitable Nirenberg-type condition, we prove the existence of at least one solution of the problem using Mawhin's coincidence degree. © 2007 Elsevier Ltd. All rights reserved.
Amster, P., De Nápoli, P., & Pablo Pinasco, J. (2008). On Nirenberg-type conditions for higher-order systems on time scales. Computers and Mathematics with Applications, 55(12), 2762–2766. https://doi.org/10.1016/j.camwa.2007.10.022